To prove that DNA is the genetic material, which radioactive isotopes were used by Hershey and Chase (1952) in their experiments?

Options

A. `.^(35)S and .^15 N`
B. `.^(32)p and .^35 S`
C. `.^(32)p and .^15 N`
D. `.^(14)N and .^15 N`

Explanation

To answer the question regarding the radioactive isotopes used by Hershey and Chase in their 1952 experiments to prove that DNA is the genetic material, we can break down the solution into the following steps:

### Step-by-Step Solution:

1. **Understanding the Experiment's Objective**:
- The primary aim of Hershey and Chase's experiment was to determine whether DNA or protein was the genetic material in bacteriophages (viruses that infect bacteria).

2. **Identifying the Components of DNA and Proteins**:
- DNA contains phosphorus but does not contain sulfur.
- Proteins contain sulfur but do not contain phosphorus.

3. **Selection of Radioactive Isotopes**:
- To differentiate between DNA and protein, Hershey and Chase used two specific radioactive isotopes:
- **Phosphorus-32 (P-32)**: This isotope was incorporated into the DNA of the bacteriophages.
- **Sulfur-35 (S-35)**: This isotope was incorporated into the proteins of the bacteriophages.

4. **Conducting the Experiment**:
- They grew one batch of bacteriophages in a medium containing P-32, allowing the DNA to become radioactive.
- They grew another batch in a medium containing S-35, allowing the proteins to become radioactive.

5. **Infection of Bacteria**:
- The radioactive phages were then used to infect non-radioactive bacteria.
- After infection, they analyzed which component (DNA or protein) entered the bacterial cells.

6. **Observing the Results**:
- They found that only the radioactive DNA (from the P-32 labeled phages) entered the bacteria, while the radioactive proteins (from the S-35 labeled phages) did not.
- This provided strong evidence that DNA is the genetic material responsible for heredity.

7. **Conclusion**:
- The radioactive isotopes used by Hershey and Chase were **P-32** (for DNA) and **S-35** (for proteins).

### Final Answer:
The radioactive isotopes used by Hershey and Chase in their experiments were **Phosphorus-32 (P-32)** and **Sulfur-35 (S-35)**.

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